1. Field of the Invention:
The present invention generally relates to a fuel supply device. More particularly, the present invention relates to a fuel supply device that supplies fuel from a fuel tank to a fuel consumption device, such as an internal combustion engine.
2. Related Art:
A system is known in which fuel pressure is maintained at a constant level by a pressure regulator. The fuel is atomized and supplied to an internal combustion engine under the controlled pressure. In this system, excess fuel resulting from fuel pressure control is returned to the fuel tank.
U.S. Pat. Nos. 5,044,344, 5,148,792, and 5,078,167 disclose a system that supplies all the fuel from a fuel tank to an internal combustion engine by means of pressure feeding. Such a system has no return route. In the system disclosed in the U.S. Pat. Nos. 5,044,344 and 5,148,792, the ability of a fuel pump is fed back and controlled according to the pressure detected by a pressure sensor. Further, a relief valve is provided in a fuel supply route to protect the fuel from excessive pressurization. However, such a fully and electronically controlled system as the above is expensive.
In contrast with such a fully and electronically controlled system, a less expensive system can be achieved by providing a pressure regulator within the fuel tank, as is disclosed in U.S. Pat. No. 5,078,167. Furthermore, even with the pressure regulator provided in the fuel tank, electronic control can also be used to reduce surplus fuel quantity discharged by the pressure regulator and save wasteful power consumption.
In such a conventional fuel supply device, however, a terminal disposed on the wall of the fuel tank is connected to the fuel pump disposed within the fuel tank via rubber piping. This type of fuel pump requires a considerable number of man-hours to install, which increases manufacturing cost.
Also, in the systems discussed above, as a check valve, a relief valve and/or a pressure regulator for preventing excessive high pressure, a projected part of the terminal is disposed on the wall of the fuel tank. Such a structure includes the problem where the shape around the discharge part of the main body of the fuel pump has to be modified. Further, due to the uniqueness of the systems, it is difficult to share many parts and components with many other fuel supply systems.
Furthermore, in the system disclosed in U.S. Pat. No. 5,078,167, the temperature of the fuel in the fuel supply route rises while the fuel pump is at a stoppage, and when the fuel pressure rises, the pressure regulator opens to lower the fuel pressure. This causes the problems of a decreasing quantity of fuel in the fuel supply route as time passes, air bubbles become mixed in the fuel or fuel vapor is generated, and as a result, when the fuel pump is restarted, fuel containing air bubbles or fuel vapor is supplied to the internal combustion engine. Such is not conducive to efficient operation of the internal combustion engine.